There has been advanced a propagation of a portable electronic device such as a cellular phone, a personal digital assistance, a notebook-size personal computer, a portable audio device, a portable visual device or the like. Conventionally, the portable electronic devices are driven by a primary battery or a secondary battery. Particularly, as the secondary battery, nickel-cadmium battery or a lithium-ion battery is used, and there has been developed a battery having a compact size and a high energy density. However, it is necessary that the secondary battery is charged for a fixed time by using a charging device after using a fixed amount of electric power. Accordingly, there has been proposed a fuel cell which does not require to be charged.
The fuel cell corresponds to an electric generator electrochemically converting a chemical energy of a fuel into an energy. As an example of the fuel cell mentioned above, there has been known a Polymer Electrolyte Fuel Cell (PEFC) generating an electric power by reducing a hydrogen gas in an anode electrode with using a perfluoro carbon sulfonic acid type electrolyte and reducing an oxygen in a cathode electrode. The PEFC mentioned above has a feature of being a battery having a high output density, and a development thereof is advanced.
However, in the hydrogen gas used in the PEFC, a volume energy density is low, it is necessary to increase a volume of a fuel tank, and an auxiliary device is necessary, the auxiliary device including a device for supplying a fuel gas and an oxidizing gas to a main body (an electric power generating portion) of the fuel cell, a humidifying device for stabilizing a battery performance and the like. Accordingly, since the fuel cell system becomes large in size, the PEFC is not suitable for a power source of the portable electronic device.
On the other hand, a direct methanol fuel cell (DMFC) generating an electric power by directly taking out a proton from a methanol has a defect that an output thereof is smaller in comparison with the PEFC mentioned above, however, it is possible to improve the volume energy density of the fuel and it is possible to reduce a number of the auxiliary device in the fuel cell main body. Accordingly, it is possible to make the cell compact. Therefore, the DMFC is remarked as a power source for the portable device, and several proposals have been made. The following reactions are performed in an anode electrode and a cathode electrode within a fuel cell main body in the DMFC.
Anode electrode: CH3OH+H2O->6H++6e−+CO2 
Cathode electrode: 6H++6e−+3/2O2->3H2O
As shown by the chemical formula mentioned above, a carbon dioxide is generated at the anode electrode side and a water is generated at the cathode electrode side by generating the electric power with using the fuel cell.
The fuel tank in the DMFC mentioned above is disclosed, for example, in the following patent document 1 or the like. The fuel tank in the prior art mentioned above is provided with a certification information, and is structured such that a main body reads the certification information so as to discriminate whether or not the fuel tank is correct, thereby controlling the power generation. Further, the document also discloses the matter that the discrimination whether or not the fuel tank is correct is executed by a computer in a remote location via a network.
Patent document 1: Japanese Unexamined Patent Publication No. 2002-280044